1. Field of the Invention
The present invention relates to a vehicular air-conditioner able to independently control the temperatures of a first air-conditioning zone and a second air-conditioning zone in a compartment of the vehicle.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-286338, there is known a vehicular air-conditioner designed to independently control the temperatures of the air blown to the driver's side and to the passenger's side in a car and the blowing modes of each side. In this related art, the target blowing temperatures were calculated from the temperature settings for the sides, the temperature of the inside air, the temperature of the outside air, etc. and these target blowing temperatures were used to control the blowing temperatures and the blowing modes.
Further, in this related art, the method used for determining the blower voltage, that is, the voltage to be applied to the blower, was to find the mean value of the target blowing temperatures and to find the blower voltage based on that mean value and the characteristics shown in FIG. 10.
If the blower temperature is determined based on the mean value of the target blowing temperatures and the characteristics of FIG. 10, the following problem sometimes occurs, however.
When the target blowing temperature of the driver's side is T.alpha. and the target blowing temperature of the passenger's side is T.beta., for example, the blower voltage corresponding to the mean value T.gamma. of T.alpha. and T.beta. (=(T.alpha.+T.beta.)/2) is determined as Va from FIG. 10. If the blower voltage is determined as Va, then, as clear from FIG. 10, enough of a flow of air is secured for the target blowing temperature of the driver's side (T.alpha.), but it is considerably smaller than the flow of air for the target blowing temperature of the passenger's side (T.beta.), that is, the blower voltage Vb.
Since the driver's side is next to the passenger's side, however, the temperatures of the two sides tend to affect each other. Therefore, independent control of the temperature of the driver's side and the temperature of the passenger's side requires that a sufficient flow of air be secured to blow to each side. If, like in the above related art, however, the voltage applied to the blower becomes considerably smaller than the blower voltage determined by either of the target blowing temperatures, it becomes difficult to independently control the temperatures of the two sides.
Also, as disclosed in the above Japanese Unexamined Patent Publication (Kokai) No. 5-286338, there is known a vehicular air-conditioner which calculates the target blowing temperatures from the temperature setting for the driver's side, the temperature setting for the passenger's side, the temperature of the inside air, the temperature of the outside air, etc. and independently controls the blowing temperatures to the sides based on these target blowing temperatures wherein, when the temperature setting for the driver's side and the temperature setting for the passenger's side were different, the target blowing temperatures were corrected in accordance with the difference of the two temperature settings so as to more precisely control temperatures of the two sides.
As mentioned above, however, it is difficult to independently control the temperature of the driver's side and the temperature of the passenger's side when the flow of air into the compartment is small. That is, if the flow of air is small, it is not possible to provide a predetermined difference to the amount of heat supplied to the individual sides unless a corresponding difference to the temperatures of the blown air is also provided. In practice, however, too much of a temperature difference given to the air blown to the individual sides is uncomfortable to the occupants of the compartment, so it is not practical to create too much of a temperature difference to the blown air.
In this way, it is difficult to independently control the temperatures of the individual sides unless there is at least a certain minimum amount of air blown. The above related art, however, makes no mention at all of this point. Accordingly, the related art might be effective when there is a certain amount of air blown, but ends up losing all meaning when the amount of air blown is small.
Also, the above type of problem does not occur only in vehicular air-conditioners for independently controlling the temperatures of the driver's side and the passenger's side. It similarly occurs in air-conditioners for independently controlling the temperatures of any first air-conditioning zone and second air-conditioning zone.